1. (Fields of the invention)
The present invention pertains to an internal grinding apparatus for grinding the surface of a long bore in a workpiece, and it particularly relates to an internal grinding apparatus which provides high cylindricality and straightness.
2. (Description of the prior arts)
Conventionally, when a long bore a of a workpiece 1 such as a plunger valve, is ground as shown in FIG. 5 and FIG. 6, the workpiece is rotated on the work head of the grinding machine, and a grinding wheel 4 provided at one end of a spindle rotor 2 through a grinding shaft (quill) 3 is also rotated at high speed. The rotating grinding wheel 4 is shifted (traversed) along the axis of rotation of the grinding wheel to thereby grind the surface of the long bore a.
However, since the quill bents during grinding work by such conventional internal grinding machine, the diameter of the long bore a of the workpiece 1 reduces as it reaches the outer end of the long bore as shown in FIG. 6, in other words, the long bore has a taper at the outer end thereof. As a result, the cylindricality and straightness are lowered.
In order to solve this problem, the applicant previously proposed a method in his own Japanese patent application No. 61-9769 which corresponds to the U.S. patent application Ser. No. 005,095 in which grinding work is carried out with the quill inclined at a predetermined angle after a point at which the quill starts bending.
However, in order to incline the quill, the mechanical clamps fastening the wheel spindle stock to the work table have to be loosened for adjusting the wheel spindle stock at a required angle using the eccentric cam, and thereafter the wheel spindle stock is fastened with the mechanical cramps again Because of this feature, this method has drawbacks: for example, it is not possible to continuously adjust the tilt angle; the mechanism is complicated; and it is difficult to make fine adjustment of the tilt angle due to backlash.